The present disclosure relates to apparatus for improved arrangements or orientations of pluralities of hydrocyclones, and particularly relates, in one non-limiting embodiment, to vessels with orientations of pluralities or groups of hydrocyclones that reduce the total size and footprint of the vessel housing them.
Hydrocyclones are well known. They are devices to classify, separate or sort liquids and/or particles in a liquid mixture based on the densities of the liquids, or in suspension based on the densities of the particles. That is, a hydrocyclone may be used to separate solids from liquids or to separate liquids or fluids of different density. A hydrocyclone will normally have a cylindrical section at the top, where liquid is being fed tangentially, and a conical base. The angle, and hence length of the conical section, plays a role in determining operating characteristics.
A hydrocyclone often has two exits on the axis thereof in opposing directions: the larger on the underflow or accept and a smaller at the overflow or reject, for instance in the case of liquid-liquid deoiling hydrocyclones. For liquid-solid hydrocyclones, the liquid overflow/accept is the relatively larger exit and the solids underflow/reject is the relatively smaller exit. The underflow is generally the denser or thicker fraction, while the overflow is the lighter or more fluid fraction. Another way of understanding a typical hydrocyclone is that it includes an elongated tapered separation chamber of circular cross-section, which decreases in cross-sectional size from a large overflow and input end to an underflow end. An overflow or reject outlet for the lighter fraction is provided at the base of the conical chamber while the heavier underflow or accept fraction of the suspension exits through an axially arranged underflow outlet at the opposite end of the conical chamber. It will be appreciated that the terms “accept” or “reject” are relative and may be reversed depending on the relative density value of the components being separated.
Liquids and suspended particles are introduced into the chamber via one or more tangentially directed inlets. These are adjacent to the overflow end of the separation chamber to create a fluid vortex therein. The centrifugal forces created by this vortex throw denser fluids and particles in suspension outwardly toward the wall of the conical chamber, thus giving a concentration of denser fluids and particles adjacent thereto, while the less dense fluids are brought toward the center of the chamber. As the denser fluids and particles continue to spiral towards the small end of the conical chamber, the lighter fractions are forced to move by differential forces in the reverse direction towards the reject outlet. The lighter fractions are thus carried outwardly through the overflow outlet. The heavier particles continue to spiral along the interior wall of the hydrocyclone and eventually pass outwardly via the underflow outlet. Internally, centrifugal forces are generated by the rapid acceleration of the fluids through the inlet ports of the hydrocyclone. As noted, denser particles or fluids migrate towards the wall for eventual exit via the underflow, whilst the less dense particles and fluids migrate towards the core, remain in the liquid and exit at the overflow through a tube typically extending slightly into the body of the cyclone at the center. Finer particles will not migrate to the center unless they are less dense than the liquid, but they will move outwards more slowly and thus may not have time to escape the center core of liquid.
The fluid velocities within a hydrocyclone are high enough that the dynamic forces produced therein are sufficiently high to overcome the effect of any gravitational forces on the performance of the device. Hydrocyclones may therefore be arranged in various physical orientations without affecting performance. Hydrocyclones are commonly arranged in large banks of several dozen or even several hundred hydrocyclones with suitable intake, overflow, and underflow assemblies arranged for communication with the intake, overflow, and underflow openings respectively of the hydrocyclones.
Earlier separator systems involving large numbers of hydrocyclone separators commonly employed complex systems of intake, overflow, and underflow pipes or conduits which occupied a substantial amount of space and which required costly and complex support structures for the piping systems involved. It is desired to reduce the space occupied by hydrocyclone assemblies and provide a relatively compact arrangement, especially in the petroleum industry, where offshore platform applications and ship-based installations put a premium on space. A compact arrangement would also minimize the cost of the equipment and improve flow distribution to the hydrocyclone inlets.
Difficulties of conventional arrangements or configurations of hydrocyclones include the fact that vessel flow capacity may be limited by the practical handling diameter of the vessel internals. Further, the inlet nozzle size may be limited by the length of the hydrocyclones. Additionally, there is difficulty in sealing in other configurations where there are an increasing number of chambers within the vessel.
There is also loss of efficiency due to poor turndown. Turndown refers to the minimum flow through the vessel that may be achieved whilst still meeting performance. The efficiency of hydrocyclones diminishes as the flow reduces so there comes a point at which the performance will not meet specifications. While it varies from case to case, typically it occurs when the flow is from about 50% to about 75% of the vessel design flow. Flow is related to the number of hydrocyclone liners in service (where the liners are defined herein as the small, individual hydrocyclones). Easily isolatable compartments are desirable to enable improved turndown characteristics.
It would be desirable if an apparatus were devised that could provide a configuration or design of a plurality of hydrocyclones that would permit smaller diameter vessels, which would thus have smaller footprints, e.g. to occupy less area on an offshore platform. Smaller diameter vessels would also dramatically reduce vessel costs in the amount of exotic materials required, e.g. stainless steel, duplex, or super duplex steels.